Since your 8 year old son has wetting accidents daily then yes your 8 year old son should wear diapers on a long road trip so that he won't wet his pants or need to stop to use the toilet.
Wearing diapers on road trips is the best thing for your kid to do as well as you if you want too.
I always wear diapers on road trips and never use the toilet when on the road trip.
I just change my diaper in the backseat of my car or in a restroom.
If your 8 year old son is wetting his pants daily then you should put him back in diapers full time.
I would also like you said treat him like a baby, give him a bottle, pacifier, crib etc.
Also when at home keep your 8 year old son just in his diaper and shirt like Tommy diaper boy in the pictures below and make him use the diapers for both poop and pee.
Your 8 year old son will learn to love his diapers if he doesn't already.
